U.S. patent number 5,612,780 [Application Number 08/660,679] was granted by the patent office on 1997-03-18 for device for detecting light emission from optical fiber.
This patent grant is currently assigned to Harris Corporation. Invention is credited to Ronald G. Boyer, Robert Rickenbach.
United States Patent |
5,612,780 |
Rickenbach , et al. |
March 18, 1997 |
Device for detecting light emission from optical fiber
Abstract
A device for determining the presence of light in an optical
fiber includes a housing having a light-receiving chamber. An
aperture in a wall of the housing accommodates insertion of the
fiber into the chamber. A brush-configured, light-blocking curtain
is mounted adjacent to the aperture and has a plurality of bristles
sized and arranged to allow an optical fiber to pass therebetween.
A funnel-shaped light reflector is disposed in the chamber adjacent
to the curtain and has a first relatively wide diameter opening at
a forward end thereof and tapers to a second, relatively narrow
diameter light-exiting opening at an apex thereof. An
opto-electronic light detector is disposed adjacent to the narrow
diameter opening of the funnel-shaped light reflector. Light
emitted by an optical fiber that has been inserted through the
bristles of the light-blocking curtain impinges upon the
opto-electronic light detector. At the same time, the bristles
effectively wrap around the fiber and prevent entry of ambient
light into the interior of the chamber and onto the light detector.
A signal processing circuit is coupled to the output of the light
detector generates an output representative of the presence of
light in the fiber in response to the measured amount of optical
energy exceeding a prescribed threshold.
Inventors: |
Rickenbach; Robert (Thousand
Oaks, CA), Boyer; Ronald G. (Camarillo, CA) |
Assignee: |
Harris Corporation (Melbourne,
FL)
|
Family
ID: |
24650524 |
Appl.
No.: |
08/660,679 |
Filed: |
June 5, 1996 |
Current U.S.
Class: |
356/73.1;
250/227.24; 385/94 |
Current CPC
Class: |
G02B
6/4214 (20130101); G02B 6/4248 (20130101) |
Current International
Class: |
G02B
6/42 (20060101); G01N 021/84 () |
Field of
Search: |
;356/73.1 ;250/227.24
;385/92,94 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: McGraw; Vincent P.
Attorney, Agent or Firm: Wands; Charles E.
Claims
What is claimed:
1. A device for detecting whether an optical transmission medium is
transmitting light comprising:
a light detector;
a light-collecting reflector which directs light impinging thereon
to said light detector; and
a brush-configured light curtain disposed adjacent to said
light-collecting reflector and being configured to allow said
optical transmission medium to pass therethrough and impinge upon
said light-collecting reflector, so that light emitted from said
optical transmission medium is directed by said light-collecting
reflector to said light detector, while preventing entry of ambient
light through said curtain.
2. A device according to claim 1, wherein brush bristles of said
light curtain are oriented generally orthogonally with respect to
the direction of insertion of said optical transmission medium into
said light-collecting reflector.
3. A device according to claim 1, wherein said light-collecting
reflector is generally funnel-shaped.
4. A device according to claim 3, wherein said generally
funnel-shaped light-collecting reflector has a first, relatively
wide diameter opening into which a terminal portion of said optical
transmission medium is insertable, and a second, relatively narrow
diameter opening at an apex of said generally funnel-shaped
light-collecting reflector, said light detector being disposed
adjacent to said narrow diameter opening of said generally
funnel-shaped light-collecting reflector.
5. A device according to claim 1, wherein said optical transmission
medium comprises one or more optical fibers.
6. A device according to claim 5, wherein said brush-configured
light curtain has a plurality of bristles that are sized and
oriented to allow said one or more optical fibers to physically
pass therethrough into said light-collecting reflector, while
blocking entry of ambient light external to said device into said
light-collecting reflector and onto said light detector.
7. A device according to claim 6, wherein said light-collecting
reflector is generally funnel-shaped.
8. A device according to claim 1, wherein said light detector is
operative to measure the amount of optical energy emitted by said
optical transmission medium inserted through said curtain into said
light-collecting reflector and to generate an output in response to
the measured amount of optical energy emitted by said optical
transmission medium exceeding a prescribed threshold.
9. A device according to claim 8, wherein said light detector is
configured to be resetable to a base energy level prior to
measuring optical energy emitted by said optical transmission
medium.
10. A device according to claim 1, wherein said light detector is
operative to detect light in a spectral range that is visible to
the human eye.
11. A device according to claim 7, wherein said brush-configured
light curtain has a plurality of bristles that are sized and
oriented to allow said one or more optical fibers to physically
pass therethrough into said generally funnel-shaped,
light-collecting reflector, while blocking entry of ambient light
external to said device.
12. A device according to claim 1, wherein said light detector is
operative to detect light in a spectral range not visible to the
human eye.
13. A device according to claim 12, wherein said spectral range
includes infrared light.
14. A device according to claim 11, wherein said brush-configured,
light-blocking curtain includes a plurality of brush-configured
light-blocking curtain heads removably mounted adjacent to said
generally funnel-shaped light reflector and having whisker-like
bristles that are arranged in overlapping relationship and oriented
generally orthogonally to the direction of insertion of said
optical transmission medium through bristles of said
brush-configured, light-blocking curtain heads into said generally
funnel-shaped light reflector.
15. A method of detecting the presence or absence of light in an
optical fiber comprising the steps of:
(a) providing a generally funnel-configured light reflector having
a relatively wide opening at a first end thereof and a relatively
narrow opening at a second end thereof;
(b) disposing a light detector adjacent to said relatively narrow
opening of said light reflector; and
(c) introducing said optical fiber into said relatively wide
opening at said first end of said generally funnel-configured light
reflector while blocking the incidence of ambient light upon said
light detector, by disposing a brush-configured, light-blocking
curtain adjacent to said relatively wide opening at said first end
of said generally funnel-configured light reflector, and inserting
said optical fiber between bristles of said light-blocking curtain,
so that an end of said optical fiber is exposed to said light
reflector, while bristles of said brush-configured, light-blocking
curtain effectively wrap around said inserted fiber, and prevent
the entry of ambient light into the interior of the funnel and onto
said light detector.
16. A method according to claim 15, wherein bristles of said
brush-configured light-blocking curtain are oriented generally
orthogonally with respect to the direction of insertion of said
optical fiber into said light funnel.
17. A method according to claim 15, wherein step (c) further
includes processing an electrical current signal produced by said
light detector so as to measure the amount of optical energy
emitted by said optical fiber inserted between bristles of said
brush-configured, light-blocking curtain into said light funnel,
and generating an output representative of the presence of light in
said optical fiber in response to the measured amount of optical
energy emitted by said optical fiber exceeding a prescribed
threshold.
18. A method according to claim 15, wherein said light detector is
operative to detect light in a spectral range that includes light
that is visible and not-visible to the human eye.
19. A method according to claim 18, wherein said spectral range
includes infrared light.
20. A device for detecting the presence or absence of light in an
optical transmission medium comprising:
a housing having a light-receiving and directing chamber, and an
aperture in a wall of said housing that is sized to accommodate the
insertion of said optical transmission medium therethrough into
said chamber;
an opto-electronic light detector disposed in said chamber and
being operative to convert light emitted by a portion of said
optical transmission medium inserted into said chamber into
electrical current;
a brush-configured, light-blocking curtain adjacent to said
aperture having a plurality of bristles that are sized and arranged
to allow said optical transmission medium inserted through said
aperture to pass between said bristles, so that light emitted by
said portion of said optical transmission medium inserted into said
chamber impinges upon said opto-electronic light detector, while
bristles of said brush-configured, light-blocking curtain
effectively wrap around said inserted optical transmission medium,
and prevent the entry of ambient light into the interior of said
chamber and onto said light detector; and
a signal processing circuit coupled to the output of said light
detector and being operative to measure the amount of optical
energy emitted by said optical transmission medium inserted between
bristles of said brush-configured, light-blocking curtain into said
chamber.
21. A device according to claim 20, wherein said signal processing
circuit includes a threshold detector circuit that is operative to
generate an output representative of the presence of light in said
optical transmission medium in response to the measured amount of
optical energy emitted by said optical transmission medium
exceeding a prescribed threshold.
22. A device according to claim 20, further including a
funnel-shaped light reflector disposed in said chamber and having a
first relatively wide diameter opening at a forward end thereof
adjacent to said brush-configured, light-blocking curtain, said
funnel-shaped light reflector tapering to a second, relatively
narrow diameter light-exiting opening at an apex of said
funnel-shaped reflector, and wherein said opto-electronic light
detector is disposed adjacent to said narrow diameter opening of
said funnel-shaped light reflector.
23. A device according to claim 20, wherein said brush-configured,
light-blocking curtain includes a plurality of brush-configured
light-blocking curtain heads removably mounted to said housing
directly behind said aperture and having whisker-like bristles that
are arranged in overlapping relationship and oriented generally
orthogonally to the direction of insertion of said optical
transmission medium through bristles of said brush-configured,
light-blocking curtain heads into said chamber.
24. A device according to claim 23, wherein said plurality of
brush-configured light-blocking curtain heads are arranged adjacent
to said aperture so that bristles thereof are partially overlapping
and mutually offset in said direction.
25. A device according to claim 23, wherein said plurality of
brush-configured light-blocking curtain heads are arranged adjacent
to said aperture so that bristles thereof are in end-to-end
abutting relationship.
26. A device according to claim 22, wherein said funnel-shaped
light reflector has a conical or curved shape, thereby directing
light emitted from said optical transmission medium toward said
light-exiting opening at said apex of said funnel-shaped reflector,
and onto said opto-electronic light detector.
27. A device according to claim 20, wherein said signal processing
circuit includes a pushbutton switch coupled in circuit with said
threshold detector circuit and being operative to controllably
reset said threshold detector circuit prior to measuring the
presence of light in said optical transmission medium.
28. A utility device comprising a housing having a chamber, and an
aperture in a wall of said housing that is sized to accommodate the
insertion of a medium therethrough into said chamber, and a
brush-configured, light-blocking curtain disposed adjacent to said
aperture having a plurality of bristles that are sized and arranged
to allow said medium to be inserted through said aperture and to
pass between said bristles, as said bristles of said
brush-configured, light-blocking curtain effectively abut against
said inserted medium and prevent the entry of ambient light into
said chamber.
29. A utility device according to claim 28, wherein said medium
comprises an optical transmission medium and further including an
opto-electronic light detector disposed in said chamber and being
operative to convert light emitted by a portion of said optical
transmission medium inserted into said chamber into an electrical
output.
30. A utility device according to claim 29, further including a
light-collecting reflector which is disposed in said chamber and is
configured to direct light emitted from said optical transmission
medium and impinging thereon to said opt-electronic light
detector.
31. A utility device according to claim 30, wherein said
light-collecting reflector comprises a generally funnel-shaped
light reflector having a first relatively wide diameter opening at
a forward end thereof adjacent to said brush-configured,
light-blocking curtain, said generally funnel-shaped light
reflector tapering to a second, relatively narrow diameter
light-exiting opening at an apex of said generally funnel-shaped
reflector, and wherein said opto-electronic light detector is
disposed adjacent to said narrow diameter opening of said generally
funnel-shaped light reflector.
Description
FIELD OF THE INVENTION
The present invention relates in general to communication systems
and test devices therefor, and is particularly directed to a
reduced complexity optical fiber radiation test device for
detecting the emission of light from the end of a light
transmission medium, in particular an optical fiber.
BACKGROUND OF THE INVENTION
In the course of servicing or testing components of a fiber optic
telecommunication system, such as identifying broken or disrupted
optical fiber strands, or identifying active fibers of a fiber
optic bundle that are to be connected to an opto-electronic
receiver, it is often necessary for a craftsperson to determine
whether one or more optical fibers of a fiber optic cable is `dark`
or `lit`, namely whether a fiber of interest is conducting light.
Since light sources used for lightwave transmission may generate
harmful laser radiation, and typically generate an output spectrum
that falls within the infrared region (e.g., 780 nm through 1600
nm) that cannot be seen by the human eye, safety precautions must
be taken, usually requiring special equipment.
For this purpose, technicians have conventionally used optical
power meters to determine the presence or absence of light within a
fiber. Unfortunately, optical power meters require that a fiber
optic connector be installed on the end of the fiber to be checked.
If such a connector is not installed, the craftsperson has nothing
more than a bare fiber optic strand with which to work. Unless the
end of the fiber is cleaved, light escaping the fiber may be skewed
and may not be directed to the detector. As a consequence, before
the fiber can be checked for the presence or absence of light, it
must be fitted with an adapter to shield the optical detector from
the incidence of ambient light (which contains infrared radiation).
This procedure is time consuming and involves expensive
equipment--the cost for a typical power meter and bare fiber
adapter may be on the order of $600 or more.
SUMMARY OF THE INVENTION
In accordance with the present invention, this problem is
successfully addressed by means of a new and improved optical
radiation detection device, that is physically configured to
readily receive or accommodate an optical fiber, regardless of the
condition of the end of the fiber, and to provide for optical
coupling of radiation present in the fiber to a light detector that
remains completely shielded from the introduction of ambient
light.
For this purpose, the optical fiber radiation detector device of
the present invention comprises a funnel-shaped reflector, having a
first relatively wide diameter opening into which a terminal
portion of an optical transmission medium, such as an individual
connectorized or bare optical fiber, or a bundle of fibers, is
insertable, and a second, relatively narrow diameter light exiting
opening at an apex of the funnel. An opto-electronic light detector
is disposed adjacent to the narrow diameter opening of the
light-reflecting funnel, and is operative to convert light that has
been collected by the funnel into electrical current. The
relatively wide diameter end of the funnel is sized so that it can
accommodate either `connectorized` fibers, bare fibers and/or
ribbon fibers.
Rather than install a rigid mechanical shutter, such as a
conventional electromechanical iris, razor blades or cloth, the
present invention uses a brush-configured light curtain head, which
is removably mounted to the test device adjacent to the wide
diameter end of the light funnel. Removable mounting of the
brush-configured light curtain head facilitates replacement of its
bristles, which may weaken with use over time, and allows the
detector window to be cleaned as part of regular maintenance.
The brush-configured light curtain is comprised of two or more
layers of opaque whisker or hair-like bristles, that are sized and
oriented generally orthogonally to the axis of the funnel and
direction of insertion of a fiber through the brush curtain into
the funnel. As a connector or fiber is being inserted, the
individual bristles of the brush curtain move out of the way and
then effectively `wrap around` an inserted fiber. This readily
allows one or more optical fibers to physically pass between the
bristles into the interior of the light funnel, so that any light
emitted from the inserted end of the optical transmission medium
will be incident upon the interior reflective sidewall of the light
funnel and directed thereby to the light detector. At the same
time, the density, depth and crosswise arrangement of the light
curtain bristles serve to block entry of ambient light external to
the device into the interior of the funnel and onto the light
detector.
Once a fiber has been inserted into through the light curtain and
into the interior of the reflector funnel, the user operates a
switch (presses a momentary closure button) to activate a photon
signal processing circuit that is coupled to the output of the
light detector. Activating this photon signal processing circuit
resets and zeroes out the detector. When the button switch is
released photon-stimulated current generated at the output of the
light detector is integrated. If, within a prescribed period of
time, e.g., approximately one to three seconds, the output of the
integrator reaches a threshold value, an output signal is
generated, for example by way of an audible tone and/or an LED
indicator. After a predetermined delay for example, approximately
three seconds, the unit turns itself OFF and is ready for another
test.
As a non-limiting example, the light detector, per se, may comprise
a semiconductor PIN (Positive Intrinsic Negative) diode which
converts each incident photon into a proportional number of
electrons. Other types of light detectors may be used, as well. The
photon generated current is integrated into an
energy-representative output voltage by means of a differential
amplifier and a low leakage capacitor. The integrated voltage will
build up in proportion to the amount of optical energy impinging
upon the light detector. Measuring energy effectively eliminates
noise and thus a false detection indication. Also, the complexity
of the circuit is reduced by using only a single amplifier.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic perspective view of the physical
configuration of an embodiment of the optical fiber radiation
detection device of the present invention;
FIG. 2 is a diagrammatic top sectional view of the device of FIG.
1;
FIG. 3 is diagrammatic side sectional view of the device of FIG. 1;
and
FIG. 4 schematically illustrates a signal processing circuit
employed in the optical fiber radiation detection device of the
present invention.
DETAILED DESCRIPTION
The physical configuration of an embodiment of the optical fiber
radiation detection device of the present invention will now be
described with reference to the diagrammatic perspective view of
FIG. 1, and the top and side diagrammatic sectional views of FIGS.
2 and 3. As shown therein, the device has a generally elongate
housing 10, sized to be held in a craftsperson's hand to facilitate
its use. The housing 10 may be comprised of a pair of rigid plastic
or metal casing halves or shells 11 and 12, which are joined
together to form a sturdy light-tight enclosure. All components of
the device, including optical, electronic and batteries are
retained within the housing 10, proper.
The housing 10 includes a front wall 13, which has an aperture 15
that is sized to accommodate the insertion of an optical
transmission medium, such as one or more connectorized fibers, bare
fibers and/or ribbon fibers, shown at 20, into an interior light
receiving and directing chamber 22. Disposed within the interior
light receiving and directing chamber 22 is a funnel-shaped
reflector 24, such as a conically shaped funnel of highly
reflective metal (e.g. chrome) or having its interior surface 23
coated with a highly reflective material, such as chrome paint. The
light reflective funnel 24 has a first relatively wide diameter
opening 26 at a forward end thereof adjacent to aperture 15, which
tapers to a second, relatively narrow diameter light-exiting
opening 28 at an apex of the funnel-configured reflector 24. An
opto-electronic light detector 29, such as a semiconductor PIN
(Positive Intrinsic Negative) diode element is disposed adjacent to
the narrow diameter opening 28 of the light-reflecting funnel 24,
and is operative to convert light that has been collected by the
reflective funnel into electrical current.
Disposed immediately behind the aperture 15 in front wall 13, and
adjacent to the relatively wide diameter opening 26 of reflective
funnel 24, are a plurality (e.g., two offset pairs) of
brush-configured light curtain heads 30, 31 and 32, 33. These
brush-configured light curtain heads are preferably configured to
be removably mounted to housing 10 directly behind the aperture 15,
and have the whisker-like bristles thereof overlap--for example,
the bristles of curtain heads 30, 31 have the ends 35, 36 partially
overlapping in a mutually axially offset, as shown in FIG. 2, and
the bristles of curtain heads 32, 33 have the ends 37, 38 thereof
disposed in abutting, end-to-end abutting relationship, as shown in
FIG. 3. As pointed out above, removable mounting of the
brush-configured light curtain heads 30, 31 and 32, 33 facilitates
replacement of their bristles, which may weaken with use over time,
and allows a detector window at the light-exiting opening 28 of the
funnel to be cleaned as part of regular maintenance.
Although the brush-configured light curtain of FIGS. 2 and 3 is
shown as comprising two pairs of brush heads, each of which has a
bundle of opaque (black) whisker or hair-like bristles, more or
less than two pairs of heads may be installed as desired, as long
as the overall effect of providing an ambient light-blocking
entryway for an optical fiber is provided. In the non-limiting
illustrated embodiment, the bristles of each head are oriented
generally orthogonally to the axis 40 of the light-reflecting
funnel 24, which effectively corresponds to the direction of
insertion of a fiber 20 through the brush curtain heads 30, 31 and
32, 33 into the funnel 24. As a result, during insertion of a
connector or fiber 20 through the brush-covered aperture 15, the
individual bristles of the brush curtain heads move out of the way
and then effectively `wrap around` the fiber.
Namely, the brush-configured light curtain allows one or more
optical fibers to physically pass between its bristles into the
interior chamber 22 of the light funnel, so that any light emitted
from the inserted end 21 of the optical fiber 20 will be incident
upon the highly reflective interior sidewall 23 of the light funnel
24 and directed thereby through exit 28 onto the light detector 29.
The opacity, density, depth and crosswise arrangement of the
bundles of light curtain bristles 30, 31 and 32, 33 thus serve to
block entry of ambient light external to light directing chamber 22
the device into the interior of the funnel and onto the light
detector 28. Because the interior surface of the reflector 24 is
tapered, e.g., curved or conically shaped, any light emitted from
the end of an inserted fiber will be directed toward the funnel's
exit aperture 28.
A signal processing circuit 40 which is coupled to the output of
the light detector 29 is schematically illustrated in FIG. 4 as
comprising an integrator 41 comprised of an operational amplifier
42 having differential (+) and (-) inputs thereof connected via a
connector 43 across PIN diode detector 29. An integrating, low
leakage capacitor 44 is coupled between the output 46 and the
negative (-) input 45 of the amplifier. A series connection of a
resistor 51 and switch contacts 53a of a momentary single-pole,
double-throw pushbutton switch 53 are coupled in parallel with
capacitor 44. The second (+) input of differential amplifier 42 is
coupled to grounded diode 47 and capacitor 48, and through resistor
49 to output 46.
The output 46 of integrator 41 is coupled through a voltage divider
57 comprised of a series connection of resistors 58 and 59 to
ground to a first input 61 of a NAND gate 60. A second input 62 of
NAND gate 60 is coupled through switch contacts 53b of switch 53 to
receive the battery power voltage V.sub.BAT (e.g., 6 V to 9 V) and
also enables logic gate 62. The output 63 of NAND gate 60 is
coupled to an output device, such as a light emitting diode 65 or
audible alarm device, not shown, which is biased by a power supply
input from a V.sub.BAT terminal 67, coupled through a resistor
69.
In operation, as light-detecting PIN photodiode 29 detects incident
photons directed thereon by reflective funnel 24, it produces an
output current whose magnitude is proportional to the number of
photons. This photon-generated output current from PIN diode 29 is
integrated into an energy-representative output voltage by
differential amplifier 42 and capacitor 44. Thus, the integrated
output voltage produced at the output of amplifier 42 will increase
in proportion to the amount of optical energy impinging upon the
light detecting diode 29. Since optical energy is measured rather
than power, noise and false detection are effectively eliminated,
as described above.
With an optical fiber 20 inserted into the light chamber 22 through
the bristles of the brush-configured light curtain, the
craftsperson operates momentary closure pushbutton switch 53, which
discharges integrating capacitor 44 and thereby resets (zeroes out)
the integrator 41. When the pushbutton switch 53 is released,
photon-stimulated current generated by light-detecting PIN diode 29
begins to be integrated. If, within a prescribed period of time,
e.g., approximately one to three seconds, the output of the
integrator reaches a threshold logic level, sufficient to change
the state of NAND gate 60, the output 63 of NAND gate 60 changes
state, thereby turning on light emitting diode 55 or supplying a
control input to another type of indication element, such as an
audible alarm device. After a predetermined delay for example,
approximately three seconds, the feedback connection to the input
of integrator 41 changes the state of its output and turns the
output indicator device OFF in preparation for testing another
optical fiber.
As will be appreciated from the foregoing description, the above
discussed need for a relatively inexpensive and reduced complexity
device that for determining the presence or absence of light within
an optical fiber (particularly where the light may be invisible to
the human eye, falling in the infrared region) is successfully
achieved in accordance with the present invention, which employs a
brush-configured light blocking curtain in combination with a
light-reflecting funnel, which physically accommodates an optical
fiber, to provide optical coupling of radiation present in the
fiber to a light detector, while simultaneously shielding the
photodetector from the introduction of ambient light.
While we have shown and described several embodiments in accordance
with the present invention, it is to be understood that the same is
not limited thereto but is susceptible to numerous changes and
modifications as known to a person skilled in the art, and we
therefore do not wish to be limited to the details shown and
described herein but intend to cover all such changes and
modifications as are obvious to one of ordinary skill in the
art.
* * * * *